1. Field of Invention
The present invention relates generally to protective enclosures for electronic circuitry.
2. Description of the Prior Art
Communication service providers are experiencing significant consumer demands to accommodate additional bandwidth and traffic capacity in existing and new communications systems. To satisfy this increasing demand, service providers have decentralized the location of equipment, added additional components, and upgraded services using improved electronics and related devices.
In decentralizing equipment, the electronics often reside at locations remote from the central office of the service provider. An objective of the service providers is to install and maintain these remotely located components for minimal costs yet maintain a highly reliable level of service from the electronics which typically have operational service lives exceeding 20 years. For utility and economic reasons, it is desirable to deploy remote electronic components outdoors in closed or sealed enclosures. Examples of the deployment of these electronics in outdoor settings varies considerably but includes locations along rural highways, along limited right-of-ways, and on metropolitan building rooftops.
Remote enclosures often house electronics having higher-power demands and greater heat-generation than earlier enclosures. Accordingly, the heat generated by each component, more so by the active than passive components, directly affects the performance of the components in the system. Since these components are generally encased or sheltered in a closed or sealed enclosure, removing the accumulated heat generated from the electronic components before a significant build-up occurs, is highly desired. Additionally, controlling the interior water vapor, in the heated air, and reducing the possibility of condensation in conjunction with the possibility of changing air temperatures inside the enclosure, has proved to be a particularly difficult problem.
There are numerous known ways of removing the heat generated within enclosures housing electronic components and circuits. However attempts to address the removal of accumulated heat in the enclosures have not been fully satisfactory. Further, attempts to prevent condensation within the enclosure occurring during power failure, for instance, have also proved generally unsatisfactory.
The failure of remotely-located electronic components can result from a range of uncontrolled or uncontrollable events including accidents, lightning strikes, power loss, vandalism, component failure, excess temperature and water vapor, i.e., humidity and condensation. Electronic units may also fail when the air temperature inside the enclosure exceeds the operational thermal limits of the electronics so that the electronics will shut down or fail. Upon operational failure, the units cool, the heated air cools such that the temperature inside the enclosure drops below the dew point, and the water vapor in the air condenses. When the failure is corrected (e.g., when power is restored) the units are again energized and will often fail due to short-circuiting occurring as a result of condensate on the energized components.
Accordingly, there exists a need to economically and simply establish and maintain the operation of electronic systems located in an enclosure during modes of operation and power failure. There exists a need to adsorb water vapor from the enclosure atmosphere during high humidity conditions and release collected water into the enclosure atmosphere as water vapor during low humidity conditions, without requiring high maintenance for the system. There exists a need to further provide low-maintenance means which are functional to provide continued operation of the electronic units before, during, and following power losses to the system.
The present invention provides a low-maintenance solution having apparatus capable of adsorbing and releasing water vapor in relation to the dew point temperature of the enclosure air in which an enclosure with heat-generating electronics is operative or undergoes power failure. The invention is further capable of reducing the likelihood of condensate forming on enclosed electronics and of regenerating its adsorptive characteristics. The invention also adaptably maintains and controls the water vapor in the enclosure during normal operational mode and in the event of power failure, virtually eliminates the likelihood of condensation on the enclosed electronic components. Frequently, and hereinafter, components of the invention are referred to as a sorption device. The sorption device has the ability to adsorb water vapor and release adsorbed water as vapor in response to the temperature within the enclosure in relation to the dew point. Further objects and advantages of this invention will become apparent from the detailed description which follows.